Friction modifiers are added to lubricants to reduce the surface friction

Friction

Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 of the lubricated parts. Typically these are polar chemical compounds having high affinity for metal surfaces and possessing long alkyl chains.

Glycerol mono-oleate is a common example of a friction modifier. Whale oil

Whale oil

Whale oil is the oil obtained from the blubber of various species of whales, particularly the three species of right whale and the bowhead whale prior to the modern era, as well as several other species of baleen whale...

 was formerly used as a friction modifier in automatic transmission fluid

Automatic Transmission Fluid

Automatic transmission fluid is the fluid used in vehicles with self shifting or automatic transmissions. It is typically colored red or green to distinguish it from motor oil and other fluids in the vehicle...

.

This additive is needed in limited slip differentials.

See also

• Oil Additive
  Oil additive
  Oil additives are chemical compounds that improve the lubricant performance of base oil . By utilizing the same base stock, many different oils can be manufactured, each with its distinctive properties. Additives comprise up to 5% by weight of some oils.Nearly all commercial motor oils contain...
  
  
• Friction Modifier